The walls of my tank are covered with white little dots which, upon closer inspection, slightly resemble hydra in shape but are alot smaller (approx. .5- 1mm in length). They seem to move with the current of the water and are only visible on the glass and not on the plants, etc. I keep three zebra danios in a 10 gal. and there seem to be no problems as of yet. Oh, and there are live plants in the tank and recently added silica sand as substrate. I looked all over the internet and had trouble finding info. Any insights would be greatly appreciated. thanks